1. Field of the Invention
This invention relates to panel displays having pel storage capability, and more particularly to a plasma panel graphics apparatus having means for updating the pel array to be shown, accurately and on a substantially real time basis.
2. Prior Art
The prior art includes numerous examples of plasma (or "gas") panel displays having selective write and erase circuits. An example is seen in U.S. Pat. No. 3,851,211. It is possible to use such prior art means to provide an all point addressable graphic display, but the burden on the data source, such as a processor, is considerable and the update rate of the image can be lower than desired for a dynamic graphic display.
Display update rates can be speeded by prior art systems which erase and rewrite the display a swath at a time, and the load on the source processor can be reduced by interposing a row buffer and a character generator between the processor and the panel assembly. Modified data tags can be used to further reduce the processing time.
3. Summary of the Invention
It is a primary object of the invention to provide a plasma panel display apparatus in which the erase-write interface to the panel subassembly is operated at its maximum data rate, while minimizing the overhead on the system processor.
According to one aspect of the invention, there is provided in a display system comprising a processor, a plasma panel subassembly including generally orthoganally related arrays of conductors and drive circuits for the same, and a read-write memory for storing the image data provided by the processor and delivering drive information to the panel subassembly, control logic for time sharing the operation of the memory between communication with the processor and with the panel subassembly, modified data tags means associated with the memory operation, and means under the control of the modified data tag means to control update, erase and write operations of the panel subassembly on an as-needed individual pel line basis.
According to another aspect of the invention, the modified data tag means are provided in memory-associated and copy registers, means are provided to scan the tag means repetitively and to freeze the status of the copy register upon a change in the content of the memory-associated register, and means are provided to carry out the erase and write operations under the control of the copy register.
According to still another aspect of the invention, there is provided a plasma display having a pel defining conductor array comprising groups of lines and line group erase means to erase (extinguish) pels of a given group in a single operation, there being means to provide a modified data tag for each line in a group containing a pel which is to be erased and means responsive to the modified data tag means to activate the line group erase means only with respect to those lines of the group which includes pels to be erased.
Other objects and advantages of the invention will be apparent from the specification and the drawings forming a part thereof.